Within the context of processing leather hides, the final color of the leather hide itself is a particularly important parameter for judging both the quality and the repeatability of the coloring processing. The latter in particular serves to give the base color to the leather hide and is carried out by means of spraying a nebulized liquid, generally a pigment, or by means of applying a paint or a fixative. In particular, it is required for the color to be homogeneously applied over the whole surface of the leather hide.
Within this context, it is also required for the leather hides to be processed, belonging to a same lot or also to two different lots, to have the same starting color gradation.
In the current state, to detect the color of the leather hide, colorimeters are used which randomly come in contact with the leather hide, or laboratory spectrophotometers are used, both arranged inside and/or downstream of the painting process.
However, these apparatuses are separate and independent from the processing plant and are not satisfactory because they require slowing down or even interrupting the processing process, with subsequent decrease in plant productivity; moreover, they require the use of dedicated personnel, with subsequent increase in costs. Indeed, the operator should pick a sample from the line and bring it to the laboratory to perform the analysis under perfectly favorable conditions.
Moreover, this type of check is performed randomly and therefore does not ensure that the color has been applied in a homogeneous, repeatable and qualitatively satisfactory manner to all leather hides processed, or in all the areas of a given leather hide.
Finally, the color detections performed often are not completely reliable and this is mainly due to the difficulty in keeping constant the distance between the system for detecting the color and the leather hide to be detected, due mainly to the flexibility and intrinsic decreased stiffness of the leather hide itself.
It is also worth pointing out that unlike other two-dimensional items, such as for example regular sheets of paper, leather hides and/or the like have a weft and a surface aspect (texture) which is not regular and repetitive, rather it is highly variable both between the different types of leather hides and within the same leather hide sample.
Therefore, it is understood how the continuous detection in line of leather hides and/or the like to date is particularly laborious and generally not reliable since it is rather frequent for the variations in color detected not to be actually present in the sample, but in reality to derive from a false detection due to the variation of textures of the sample leather hide itself and/or to the presence of creases or surface defects.
To this end, it is worth noting that EP1935646 describes a device used for checking, more than for measuring, the color of the upper sheet of a stack of paper sheets which, as mentioned, are not similar to leather hides and/or the like. In particular, the device comprises a movable body in which a sensor is mounted, which conveniently is positioned and moves so as to detect the color data of a print control strip which is specifically printed in color by a traditional offset printing machine, on said sheets stacked on top of one another.